Respirable Crystalline Silica Exposure-Response Evaluation of Silicosis Morbidity and Lung Cancer Mortality in the German Porcelain Industry Cohort

Objective: To quantify silicosis and lung cancer risks among porcelain workers occupationally exposed to respirable crystalline silica. Methods: We reread historical radiographs to identify silicosis and estimated exposure on the basis of detailed work history and about 8000 industrial hygiene measurements. Cox proportional hazards models estimated risks by cumulative and average exposure. Results: Adjusted silicosis hazards ratios were 5.3 (95% confidence interval [CI], 1.6 to 17.3); 7.3 (95% CI, 2.6 to 20.8); and 6.8 (95% CI, 3.0 to 15.3) for cumulative exposures > 4 to 5; > 5 to 6; and > 6 mg/m(3)-years, and 3.3 (95% CI, 0.8 to 14.7), 13.6 (95% CI, 4.2 to 44.4) and 23.2 (95% CI, 8.2 to 65.8) for average exposures > 0.1 to 0.15; > 0.15 to 0.2 and > 0.2 mg/m(3), respectively. Exposure was not associated with any cause of death including lung cancer. Conclusions: Respirable crystalline silica exposure more than 4 mg/m(3)-years (cumulative) or more than 0.15 mg/m(3) (average) were strongly associated with silicosis, but unrelated to lung cancer risks.